Black Friday bargain hunters at Wal-Mart will have to wait in-store for up to five hours before taking their mid-size TVs, lower-end laptops and cameras home, under a holiday promotion the giant discount chain unveiled yesterday.

The retailer said it will open at midnight Friday for an “open house” with limited, deep discounts — but would not markdown many of the must-have electronics until 5 a.m.

“Wal-Mart invites customers to come in and stay for the season’s hottest consumer electronics savings,” the chain said in a statement. That means shoppers will have to walk around the store, with gifts in hand, perhaps, until the lower prices kick in shortly before dawn.

This year marks the first time that Wal-Mart — which got into hot water in 2008 when a worker was trampled to death while opening the doors on Black Friday at a store in Valley Stream, LI — will open at midnight Friday instead of 5 a.m.

Bigger-ticket deals traditionally associated with Black Friday — such as a 46-inch Sony flat-screen TV for $698 — won’t be available until Saturday.

Overall, when it comes to shopping, Thanksgiving is the new black — Black Friday, that is.

The day after Thanksgiving has traditionally marked the start of the holiday shopping season, but early-bird specials on Friday increasingly are giving way to stores opening on Thanksgiving itself — before the bird is cold. Toys “R” Us, which opened its doors at midnight Friday last year, will be open at 10 p.m. on Thanksgiving this year.

“There were huge lines when we opened at midnight last year — after eating dinner, people are looking for something to do,” Toys “R” Us CEO Jerry Storch told The Post. “We thought, ‘Why not just let them come in and shop earlier?’ ”

For nearly 20 years, Kmart has been unusual with a policy to open its doors on Thanksgiving. But this year, Sears will open its doors on Thursday morning. Likewise, Gap is dramatically expanding the number of Gap and Old Navy stores that will be open on Turkey Day.

Overall, this year’s discounts won’t be as dazzling as in years past because retailers have made more cautious bets on holiday inventory, says Kevin Strawbridge of Dealtaker.com, an online shopping site.

“Last year, the discounts were averaging in the 25- to 30-percent range, but this year we’re seeing 15 to 20 percent,” Strawbridge said, noting that the trend has been consistent throughout clothing, electronics and appliance stores.